Column holdown connection

ABSTRACT

A connection between a metal column, in particular a vertical I-beam, and an underlying structural member, in particular a ferroconcrete foundation, using a connector that is fastened to the metal column using both bolts and screws.

BACKGROUND OF THE INVENTION

This invention relates to a connector for anchoring a first building structural member to a second building structural member. The connector works in conjunction with a separate anchor member that is received by or is attached to the second building structural member and fastener means for attaching the connector to the first building structural member.

Earthquakes, hurricanes, tornadoes, and floods impose forces on a building that can cause structural failure. To counteract these forces, it has become common practice to strengthen or add ties between the structural members of a building in areas where such cataclysmic forces are typically focused. For example, framed walls can be attached to the foundation instead of merely resting on it. The connections between the framed walls of each floor can be strengthened. And joists can be connected to both their headers and the support member for their header. One of the most common connectors designed for strengthening structural connections in called a holdown by the inventor. Holdowns are commonly used to anchor framed walls to the foundation.

Early holdowns where constructed from two or more separate pieces of metal, and the pieces were welded together. These holdowns had to be painted to resist rusting because welding destroys the zinc coating of galvanized sheet metal. They were heavy and costly to produce because of the additional manufacturing steps and manual labor involved in welding and painting operations.

State of the art holdowns are made from galvanized sheet metal formed on progressive die machines and require no welding or painting. These advancements have reduced the cost of making holdowns while increasing their ability to withstand tension forces. However, ongoing research and development have demonstrated that it is possible to produce holdowns that are more inexpensive to produce and stronger for many connections.

Most of the holdown connectors of the prior art that work in conjunction with a separate anchor member work in a similar fashion. The anchor member, which is attached to the second structural member, attaches at the seat of the connector. This seat is connected to a back member. The back member attaches to the first building structural member, generally a stud in a framed wall. Most holdown connectors have one or more side members to increase the strength of the connector or to connect the seat member to the back member.

Most prior art holdown connectors that attached to a separate anchor member share a common characteristic: they attach to the vertical structural member with one type of fastener, either bolts or screws. If only screws are used, a large number must be distributed over a correspondingly large part of the connector because screws have relatively low bearing strength. The part of the connector devoted to accepting fasteners must, therefore, be either relatively broad, long, or some compromise between the two. Such a connector cannot fit in a very restricted space.

The holdown connector of the present invention is specifically designed to fit within a restricted space. In order to do so, it uses a plurality of bolts in order to achieve relatively high load resistance. However, in the preferred embodiment, testing has revealed that the bolts alone would be insufficient to adequately resist rotation and deflection and a connection made with bolts alone would therefore be inadequate.

Because rotation and deflection forces are less substantial that tension forces, and because space in the preferred embodiment is limited, the bolts are augmented with screws that resist rotation and deflection in a novel combination.

There is still a continuing need in the art for a connector that can be made more inexpensively, installed more easily, and with better withstands forces imposed by cataclysmic events.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a connection between a metal column and an underlying structural member. This object is achieved by providing a connector that is fastened to the metal column in a unique manner, using both bolts and screws.

An object of the present invention is to provide a connection between an I-beam and an underlying structural member. This object is achieved by providing a connector that attaches to the web of the I-beam.

An object of the present invention is to provide a connection between an I-beam and an underlying structural member that does not interfere with adjacent structural members. This object is achieved by providing a connector that fits between the side members of the I-beam.

An object of the present invention is to provide a connection between an I-beam and an underlying structural member that resists rotation and deflection. This object is achieved by providing a connector that attaches to the web of the I-beam with bolts and screws spaced to either side of the bolts.

An object of the present invention is to provide a connection between a metal column and an underlying structural member that is both quick and easy to make. This object is achieved in part by using self-drilling screws.

An object of the present invention is to provide a connection between a metal column and an underlying structural member that is inexpensive. This object is achieved in part by providing a connector that can be made from sheet steel.

An object of the present invention is to provide a connection between a metal column and an underlying structural member that resists fire, corrosion and infestation. These objects are achieved by providing a connection that can be made entirely out of metal and concrete. These and other objects of the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a connection formed in accordance with the present invention.

FIG. 2 is a top plan view of the connector of the present invention.

FIG. 3 is a front elevation view of the connector of the present invention.

FIG. 4 bottom plan view of the connector of the present invention.

FIG. 5 is a back elevation view of the connector of the present invention.

FIG. 6 is a left side elevation view of the connector of the present invention.

FIG. 7 is a right side elevation view of the connector of the present invention.

FIG. 8 is a cross-section view of a connection formed in accordance with the present invention.

FIG. 9 is a cross-section view of the column and connector of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As best shown in FIGS. 1 and 8, the present invention is a column holdown connection 1 in a building 2. The connection 1 comprises, basically, an underlying structural member 3, an anchor 4, a substantially vertical metal column 6, and a holdown connector 8. The anchor 4 is restrained by the underlying structural member 3. The anchor 4 has an attachment end 5 protruding above the underlying structural member 3. The substantially vertical metal column 6 has a bottom end 7 supported by the underlying structural member 3. The holdown connector 8 has a back member 9 and a seat member 10. The back member 9 is fastened to the column 6 with a plurality of bolts 11 and a plurality of screws 12. The seat member 10 is restrained by the attachment end 5 of the anchor 4.

As best shown in FIGS. 1 and 8, preferably the underlying structural member 3 is a foundation 3. More preferably, the the foundation 3 is cementitous. In the most preferred embodiment, the foundation 3 is concrete reinforced with steel rebar. Alternatively, the underlying structural member 3 could be the floor 3 of an upper storey. In such a case, the anchor 4 could be restrained through a second holdown connector 8, an arrangement common in floor-to-floor connections.

As best shown in FIGS. 1 and 8, the anchor 4 is preferably an anchor bolt 4, specifically a ⅞ inch anchor bolt. Most preferably, the anchor is a bent steel bolt 3 embedded in a ferroconcrete foundation 3.

As best shown in FIGS. 2 and 4, preferably the seat member 10 of the holdown connector 8 is formed with an anchor opening 13 through which the attachment end 5 of the anchor 4 passes. The attachment end 5 of the anchor 4 preferably has helical threads 14 and a nut 15 is threaded onto the helical threads 14, thereby restraining the attachment end 5 against the seat member 10. Alternatively, the attachment end 5 of the anchor 4 could be welded to the holdown connector 8 or otherwise fixed.

As best shown in FIGS. 1 and 8, the column 6 is preferably an I-beam 6 with a central, substantially planar web member 16 having a first side 17 and a second side 18, a first substantially planar side member 19 and a second substantially planar side member 20. Preferably, the first side member 19 and the second side member 20 are generally perpendicular to the web member 16 and extend beyond both the first side 17 and the second side 18 of the web member 16 to create a pair of back-to-back channels 21. Alternatively, the column 6 could be a hollow, tubular column 6 or even a thick, solid block 6.

As best shown in FIG. 8, preferably the column 6 is formed with a plurality of bolt openings 22 in the web member 16 adjacent the bottom end 7. The holdown connector 8 is preferably formed with a plurality of bolt openings 23 in the back member 9. And, preferably, the plurality of bolts 11 passes through the plurality of bolt openings 23 in the back member 9 of the holdown connector 8 and through the plurality of bolt openings 22 in the column 6.

As best shown in FIGS. 8 and 9, the bolt openings 22 in the column 6 are preferably slotted openings 22, each with a horizontal diameter 33 and a vertical diameter 24, the horizontal diameter 33 being greater than the vertical diameter 24. This would allow for horizontal adjustment of the holdown connector 8 relative the column 6 and the anchor 4. Most preferably, the horizontal diameter 33 is 1.25 inches and the vertical diameter 24 is 0.8125 inches.

As best shown in FIGS. 3 and 5, preferably the bolt openings 23 in the back member 9 of the holdown connector 8 are round, so that there is as little play as possible between the bolts 11 and the bolt openings 23.

As best shown in FIGS. 3 and 5, the back member 9 of the holdown connector 8 is preferably formed with a plurality of screw openings 25. Preferably, the plurality of screws 12 passes through the plurality of screw openings 25 in the back member 9 of the holdown connector 8 and into the web member 16 of the column 6. Alternatively, holes could be drilled through either the holdown connector 8, the column 6, or both at the time of installation, either with a drill bit or with self-drilling screws 12. The screws 12 of the plurality of screws 12 are preferably self-drilling screws 12, whether or not holes are prepared in the holdown connector 8 and the column 6. Preferably, the screws 12 of the plurality of screws 12 are also self-tapping screws 12. Most preferably, the screws 12 are #14 self-drilling screws.

As best shown in FIGS. 1 and 8, the bottom end 7 of the column 6 preferably rests on a substantially horizontal bottom plate 26, and the bottom plate 26 rests on the underlying structural member 3. Preferably, the bottom plate 26 is a channel 26 having two side members 27 and a bottom member 28, the two side members 27 embracing the bottom end 7 of the column 6. Alterntively, the column 6 could rest directly on the underlying structural member 3, with or without a discontinuous bottom plate 26 to either side of the column 6.

As shown in all the drawing figures, preferably,\ the back member 9 of the holdown connector 8 is substantially planar and substantially vertical. The seat member 10 of the holdown connector 8 preferably is substantially planar and substantially horizontal. These are essentially the simplest forms for the back member 9 and seat member 10 and therefore the easiest and most economical to manufacture and install.

As best shown in FIGS. 1, 2, 3 and 4, the back member 9 and the seat member 10 preferably are integrally joined, either by being bent out of the same sheet material or cast in the same mould, or by being welded together. Alternatively, the back member 9 and seat member 10 could be mechanically interlocked, either directly with each other or through other intervening parts of the holdown connector 8.

As best shown in FIG. 1, preferably the back member 9 and the seat member 10 are joined by a first side member 29 substantially orthogonal to both the back member 9 and the seat member 10. More preferably, the back member 9 and the seat member 10 are joined by a second side member 30, the second side member 30 being substantially orthogonal to both the back member 9 and the seat member 10. The first side member 29 and the second side member 30 preferably are substantially planar. Preferably, the back member 9 and the seat member 10 are generally rectangular while the first side member 29 and the second side member 30 are substantially triangular.

As best shown in FIG. 1, the back member 9 of the holdown connector 8 preferably fits entirely between the first side member 19 and the second side member 20 of the column 6. If the column 6 is, or has, a channel 21, it is advantageous to nest the holdown connector 8 within the channel 21 in order to come as close as possible to horizontally centering the holdown connector 8 to come as close as possible to perfectly concentric loading.

As best shown in FIG. 1, preferably the column 6 is a wall stud 6. In the most preferred form of the invention, the column is sufficiently narrow to fit within the space of a standard light frame wall, which is framed with nominal 2×4 wood studs when wood is the primary construction material.

As best shown in FIGS. 1 and 8, the bolt openings 22 in the web member 16 of the column 6 preferably are substantially vertically aligned. Most preferably, four bolt openings 22 in the web member 16 of the column 6 are used for the present invention. Most preferably, the lowest of these bolt openings is 6.25 inches from the bottom end 7 of the column 6 and the bolt openings 22 are 2.75 inches apart on center.

As best shown in FIGS. 1, 3 and 5, preferably the plurality of screws 12 are horizontally spaced to either side of the bolt openings 22 in the web member 16 of the column 6, in order to resist deflection and rotation.

The column 6 is preferably formed from steel, although any other material of sufficient strength and other requisite attributes could be used. Preferably, the holdown connector 8 is formed at least in part by cutting sheet steel. Cold forming connectors from sheet steel is common because of steel's malleability. The steel is preferably galvanized, but it can also be stainless, a more expensive alternative. The holdown connector 8 could be formed at least in part by casting metal. The most common metal for cast connectors is aluminum, because of its combination of light weight, resistance to corrosion, cost and the ease with which it is cast.

As best shown in FIG. 9, preferably the holdown connector 8 is formed with planar metal members 31 and the column 6 is formed with planar metal members 32 and the planar metal members 32 of the column 6 are thicker than the planar metal members 31 of the holdown connector 8.

Although the present invention is discussed as a holdown connection 1 basically comprising an underlying structural member 3, an anchor 4, a substantially vertical metal column 6, and a holdown connector 8, the holdown connector 8 of the present invention, like many prior art holdown connectors 8, could be oriented horizontally on a beam analogous to the metal column 6, anchored either to an adjacent structural member such as a wall or beam analogous to the underlying structural member 3. The connection 1 would be essentially the same, simply turned 90 degrees onto its side. The anchor 4 could be restrained through attachment to a second horizontally-oriented holdown connector 8, as in a vertical floor-to-floor tie connection. 

1. A column holdown connection (1) in a building (2), said connection (1) comprising: a. an underlying structural member (3); b. an anchor (4) restrained by said underlying structural member (3), said anchor (4) having an attachment end (5) protruding above said underlying structural member (3); c. a substantially vertical metal column (6) with a bottom end (7) supported by said underlying structural member (3); d. a holdown connector (8) having a back member (9) and a seat member (10), said back member (9) being fastened to said column (6) with a plurality of bolts (11) and a plurality of screws (12), and said seat member (10) being restrained by said attachment end (5) of said anchor (4).
 2. The connection (1) of claim 1 wherein: a. said underlying structural member (3) is a foundation (3).
 3. The connection (1) of claim 2 wherein: a. said foundation (3) is cementitous.
 4. The connection (1) of claim 1 wherein: a. said anchor (4) is an anchor bolt (4).
 5. The connection (1) of claim 4 wherein: a. said seat member (10) of said holdown connector (8) is formed with an anchor opening (13) through which said attachment end (5) of said anchor (4) passes; and b. said attachment end (5) of said anchor (4) has helical threads (14) and a nut (15) is threaded onto said helical threads (14), thereby restraining said attachment end (5) against said seat member (10).
 6. The connection (1) of claim 1 wherein: a. said column (6) is an I-beam (6) with a central, substantially planar web member (16) having a first side (17) and a second side (18), a first substantially planar side member (19) and a second substantially planar side member (20), said first side member (19) and said second side member (20) being generally perpendicular to said web member (16) and extending beyond both said first side (17) and said second side (18) of said web member (16) to create a pair of back-to-back channels (21).
 7. The connection (1) of claim 6 wherein: a. said column (6) is formed with a plurality of bolt openings (22) in said web member (16) adjacent said bottom end (7); b. said holdown connector (8) is formed with a plurality of bolt openings (23) in said back member (9); and c. said plurality of bolts (11) passes through said plurality of bolt openings (23) in said back member (9) of said holdown connector (8) and through said plurality of bolt openings (22) in said column (6).
 8. The connection (1) of claim 7 wherein: a. said bolt openings (22) in said column (6) each have a horizontal diameter (33) and a vertical diameter (24).
 9. The connection (1) of claim 8 wherein: a. said bolt openings (23) in said back member (9) of said holdown connector (8) are round.
 10. The connection (1) of claim 7 wherein: a. said back member (9) of said holdown connector (8) is formed with a plurality of screw openings (25); and b. said plurality of screws (12) passes through said plurality of screw openings (25) in said back member (9) of said holdown connector (8) and into said web member (16) of said column (6).
 11. The connection (1) of claim 10 wherein: a. said screws (12) of said plurality of screws (12) are self-drilling screws (12).
 12. The connection (1) of claim 11 wherein: a. said screws (12) of said plurality of screws (12) are self-tapping screws (12).
 13. The connection (1) of claim 1 wherein: a. said bottom end (7) rests on a substantially horizontal bottom plate (26), and said bottom plate (26) rests on said underlying structural member (3).
 14. The connection (1) of claim 13 wherein: a. said bottom plate (26) is a channel (26) having two side members (27) and a bottom member (28), said two side members (27) embracing said bottom end (7) of said column (6).
 15. The connection (1) of claim 1 wherein: a. said back member (9) of said holdown connector (8) is substantially planar. and substantially vertical; b. said seat member (10) of said holdown connector (8) is substantially planar and substantially horizontal.
 16. The connection (1) of claim 15 wherein: a. said back member (9) and said seat member (10) are integrally joined.
 17. The connection (1) of claim 16 wherein: a. said back member (9) and said seat member (10) are joined by a first side member (29) substantially orthogonal to both said back member (9) and said seat member (10).
 18. The connection (1) of.claim 17 wherein: a. said back member (9) and said seat member (10) are joined by a second side member (30), said second side member (30) being substantially orthogonal to both said back member (9) and said seat member (10).
 19. The connection (1) of claim 18 wherein: a. said first side member (29) and said second side member (30) are substantially planar.
 20. The connection (1) of claim 19 wherein: a. said back member (9) and said seat member (10) are generally rectangular.
 21. The connection (1) of claim 21 wherein: a. said first side member (29) and said second side member (30) are substantially triangular.
 22. The connection (1) of claim 6 wherein: a. said back member (9) of said holdown connector (8) fits entirely between said first side member (19) and said second side member (20) of said column (6).
 23. The connection (1) of claim 1 wherein: a. said column (6) is a wall stud (6).
 24. The connection (1) of claim 7 wherein: a. said bolt openings (22) in said web member (16) of said column (6) are substantially vertically aligned.
 25. The connection (1) of claim 24 wherein: a. said plurality of screws (12) are horizontally spaced to either side of said bolt openings (22) in said web member (16) of said column (6), in order to resist deflection and rotation.
 26. The connection (1) of claim 1 wherein: a. said column (6) is formed from steel.
 27. The connection (1) of claim 1 wherein: a. said holdown connector (8) is formed at least in part by cutting sheet steel.
 28. The connection (1) of claim 1 wherein: a. said holdown connector (8) is formed at least in part by casting metal.
 29. The connection (1) of claim 1 wherein: a. said holdown connector (8) is formed with planar metal members (31) and said column (6) is formed with planar metal members (32) and said planar metal members (32) of said column (6) are thicker than said planar metal members (31) of said holdown connector (8). 